Fukushima Watch: Questions and Answers on Contaminated Water

This aerial photo taken in August 2013 shows the Fukushima Daiichi nuclear plant. From bottom to top, reactors 4, 3, 2, 1, 5, and 6 are seen.

AP/Kyodo

Tuesday marks three years since an earthquake and tsunami in Japan led to the world’s worst nuclear accident since Chernobyl. After a year in which leaks of contaminated water at the Fukushima Daiichi nuclear-power plant made headlines, here are some questions and answers on where the issue stands:

Q: Is the water problem fixed?

A: Not yet. A large amount of groundwater keeps flowing under reactors that suffered meltdowns, creating about 400 metric tons a day of highly contaminated water. The existing water cleaning system removes almost all radioactive cesium from it, but other radioactive materials remain. A new water cleaning system called ALPS has been proved in a laboratory to remove all radioactive materials except tritium, which is less harmful, but ALPS has not yet worked fully at the site. Getting it to do so is a top priority for Tepco.

Q: Even if the new water cleanser works, is it safe to dump water with tritium?

A: Tritium exists naturally, and nuclear power facilities across the world discharge tritium water into the environment. The International Atomic Energy Agency recommended late last year that Tepco consider discharging tritium water in a controlled way as an option so it can focus on other issues that pose bigger risks. However, local fishermen are adamantly opposed. They have already suffered huge damage to their business and fear a further hit to the reputation of Fukushima fish.

Q: Is there any health risk for people on North America’s West Coast?

A: Probably not, say experts.

The question was raised by the town council of Fairfax in the San Francisco Bay Area. On Nov. 6, it adopted a resolution that calls for United Nations intervention in the Fukushima cleanup, saying contaminated water posed “health and safety concerns to America’s West Coast.” The city of Berkeley, Calif., followed with a similar resolution Dec. 3.

Most radioactive materials in the water dumped into the sea right after the accident have passed their half-lives or fully disappeared, so only cesium 137 and strontium 90 are real risks when it comes to ocean contamination, said Tamotsu Kozaki, a Hokkaido University expert on radioactive waste management. Of the two, cesium has a strong tendency to stick to soil and is likely to remain in the mud on the ocean bed near Fukushima, he said. Strontium 90 is more dangerous because it tends to accumulate in animal bones, but it’s unlikely for a single fish passing near the plant to capture enough to reach dangerous levels, said Mr. Kozaki.

Hiroaki Koide, a nuclear-power critic and assistant professor at Kyoto University, said some radioactive materials were likely to reach the U.S. West Coast, but he said the amount was small compared to the radioactive releases by nuclear-arms tests in the 1960s and unlikely to pose a big health risk.

Q: Isn’t it safer to encase the three reactors that suffered meltdowns with concrete walls and roofs like Chernobyl?

A: Opinions vary. Some experts say concrete casing would prevent new water from flowing into the most damaged parts of the plant, among other benefits. Mr. Koide said the idea would minimize workers’ exposure to radiation and could work so long as air-cooling of the reactors is possible. But Shunichi Tanaka, Japan’s top nuclear regulator, said even waiting 100 years wouldn’t significantly lower the risks posed by melted fuel. “Uranium and plutonium have a very, very long half-life. Playing for time would make little difference,” Mr. Tanaka said.

Q: Is there any other way to cut the water flow into the reactors?

A: The government is preparing to build underground ice walls around the first three reactors to block fresh water from flowing into them. The work will begin as early as this month and the ice walls encasing the reactors will be formed around spring in 2015, according to the government. Sumio Mabuchi, a lawmaker who has dealt with the contaminated water issue, proposes building another underground wall with a kind of concrete to prevent water from seeping in.

Separately, Tepco has been coating the seabed in the bay next to the plant with a kind of clay used in construction to prevent radioactive cesium trapped in the soil there from mixing with seawater. And an attempt to remove strontium from the soil in the site is under way.

For more on Fukushima cleanup risks including the removal of melted fuel, check out this article.

Corrections & Amplifications:The International Atomic Energy Agency recommended late last year that Tokyo Electric Power Co. consider discharging water with tritium in a controlled way as an option. An earlier version of this post incorrectly said the IAEA recommended that Tepco discharge the tritium water in a controlled way.

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